Auto Generated USDZ flipped Normals

[CrystalDesignMT]

Description

When opening QuickLook with certain GLB's (exported by BABYLONJS) the auto-generated USDZ has flipped normals, causing Backface-Culling to render wrong faces.
If i flip the Normals on the Model myself it is wrong in the 3D Scene but right in QuickLook AR.

As said this only happens on certain Models but i can't tell why, it certainly is a bug on one side ModelViewer or QuickLook but if you could tell why these Models are affected that could also be sufficient.

Live Demo

https://glitch.com/edit/#!/boatneck-twisty-bellusaurus?path=index.html%3A40%3A0

Version

• model-viewer: v3.2.1

Browser Affected

• Chrome, version: xx.x.xxxx.xx
• Edge
• Firefox
• IE
• Safari

OS

• Android
• iOS
• Linux
• MacOS
• Windows

AR

• WebXR
• SceneViewer
• QuickLook

[elalish]

Actually, I would say it's most likely a bug in the three.js USDZExporter, @mrdoob. Thanks for including the repro model!

[hybridherbst]

Adding myself here 👀
There's no bug opened on the three.js side yet, right?

[elalish]

Not that I'm aware of.

[CrystalDesignMT]

Ok seems like a WebGLRenderer <-> QuickLook thing as explained in the three.js issue where they handle negative scaling differently.
I guess nothing one can do here other than avoiding negative scaling.